Over the past several years our multidisciplinary research team has been dedicated to discovering and validating candidate early detection biomarkers for breast and ovary cancers. We are now in an ideal position to lead an EDRN CVC for several reasons: 1. We have lists of promising breast and ovary cancer early detection biomarkers that have been evaluated in Phase 1 to early Phase 3 validation studies that warrant further investigation in Phase 3 studies;2. We have developed considerable expertise in the design, conduct, analysis, and interpretation of cancer biomarker discovery and validation studies;3. Over the course of four work we have developed or gained access to a large number of high quality well-characterized breast and ovary cancer sample repositories that we are willing to share with EDRN;and 4. We have a long history of leading and supporting collaborative projects that have involved shared samples, and we have procedures in place to facilitate the processing and tracking of specimen requests. Herein we propose a new prospective collection of preclinical specimens from breast cancer cases and controls which is unique in that it will include detailed mammography information. We also propose a series of primarily Phase 3 validation studies. For breast cancer we will conduct a Phase 3 study beginning in Year 1 (Study 1) and then plan to design a series of Phase 2 and 3 studies in Years 4-5 (Study 5) as candidates from our work and others in EDRN mature. The primary specific aim of Study 1 is to conduct a second screen of promising candidates identified in a large discovery project using preclinical samples, and to then validate the top candidates in an independent set of preclinical samples from WHI. For ovary cancer we propose a consecutive series of three Phase 3 studies over Years 1-3. Several ovary cancer biomarkers have been validated, but none achieve clinically useful performance on their own. Thus, Study 2 is a Phase 3 validation aimed at validating and refining two- and four-marker algorithms using serial preclinical samples from the PLCO trial. Study 3 will further validate specific screening decision rules in preclinical serial samples from the UKCTOCS trial. Based on Studies 2 and 3, Study 4 will validate ovary cancer markers and screening decision rules in an independent set of WHI serial preclinical samples, a setting in which no ovary cancer screening occurred.